1. Field of the Invention
The present invention relates to a pressurizing apparatus for polishing end faces of fine workpieces, and more particularly to an end face polishing apparatus for polishing to a spherical form a ferrule end face as a connector component part of an optical fiber.
2. Description of the Related Art
In recent years, optical communication is expected to become the next generation communication technology because of its high capacity and speed. Optical fibers have been introduced into our surroundings. The ferrules are formed of zirconia based ceramic material into a cylindrical form through an injection molding, extrusion or pressing technique, and used as major optical connector parts for optical fibers. Here, the ferrule has its hollow portion termed as a fiber insertion bore in which an optical fiber is inserted. Such ferrules are abutted against each other at their end faces thereby providing coupling between optical fibers. In coupling optical fibers, there is a necessity to polish ferrule end faces to a high surface roughness accuracy in order to prevent light from reflecting and attenuating at abuttment faces of the ferrules and keep a fiber optical characteristic favorable.
Conventionally, when polishing an end face of a ferrule, the ferrule has been fixed by a jig plate. Thereafter, the ferrule at an end face is pressed onto a polishing sheet that is elastically deformable by given pressure (load weight, spring force) and then the polishing sheet is rotated. By utilizing a spherical depression surface on the polishing sheet resulting from pressing the ferrule end face, the ferrule end face is polished to a spherical shape through three stages of rough, middle and fine finishes.
The conventional polishing apparatus have not had a means to control the pressure at which the ferrule end face is urged against the polishing sheet during polishing of the ferrule end face. As a result, the ferrule end face has to be urged onto the polishing sheet at a given high pressure for polishing into a spherical shape. Consequently the ferrule end face is burdened with a high application of pressure at the start of polishing operation, resulting in damage to the ferrule end face.